1. Field of the Invention
Embodiments of the invention generally relate to methods and apparatus for use in exhaust manifold assemblies of large diesel engines, such as engines for ships, locomotives and the like. More particularly, the invention relates to a screen for protecting a turbocharger of a diesel locomotive.
2. Description of the Related Art
Turbo screens are utilized in the exhaust manifolds of diesel locomotives to prevent failed engine parts or other debris from entering and damaging the turbo charger. Typically, turbo screens are subject to temperature cycling during operation due to the temperature changes of exhaust gas flowing through the turbo screen at different engine settings during use. Exhaust gases of a locomotive engine can quickly go from relatively low temperatures at idle setting to higher temperatures at higher notch settings. However, such a temperature change is not instantly homogeneous in the system, with the center of the turbo screen reaching the higher temperatures more quickly than the outer radial section which remains at lower temperatures. Conventional turbo screens are fabricated from a perforated, thick steel flat plate in order to have sufficient impact resistance. Due to the temperature cycling, the apertures perforating the steel flat plate are typically arranged in a radial flowered pattern, such that the center region has a low, open area as compared to the radial area. The radial flowered pattern is used because the pattern has demonstrated a resistance to cracking during the life of the turbo screen, which other patterns are prone to failure. However, the radial flowered pattern also contributes to high pressure drop which adversely affects engine performance of the diesel locomotive. Moreover, the thick material needed to obtain the impact resistance makes the steel flat plate turbo screen expensive. Therefore, there is a need for an improved turbo screen.